Filament-winding compositions for fiber/resin composites

ABSTRACT

Resin compositions useful for filament winding applications comprising an epoxy component including at least one polyepoxide resin curable by heat, an olefinicially unsaturated monomer component including at least one polyolefinically unsaturated monomer curable by actinic radiation, at least one photoinitiator, at least one organic peroxide, and a heat activated curing agent for epoxides. The compositions have a viscosity less than about 2000 centipoise (cps) and are capable of retaining this viscosity for at least about 2 hours at a temperature of from about ambient temperature to about 60° C. The resins are capable of being immobilized by actinic radiation exposure and further heat cured without substantial resin drip. One or more organic peroxides are employed, selected from the group of organic peroxides having 10 hour decomposition half lives at temperatures of from about 50° C. to less than about 104° C. Also, fiber resin composites comprising fiber substrates impregnated with the dual-curing resin compositions. Also the process for coating fiber substrates with the dual-curing resin compositions is disclosed.

This application is a division of Ser. No. 08/036,325 filed Mar. 24,1993, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to fiber/resin composites and tomethods of making such composites. In a specific aspect, the presentinvention relates to resin articles comprising arrays of continuousfilaments, such as are formed by filament winding, prepregs and thelike.

2. Description of the Related Art

In the field of composite materials, a variety of fabrication methodsand techniques have come into usage for producing fiber-reinforced resinmatrix materials. Continuous filament processes have evolved which areadapted to automated production of filament-reinforced resin articles.The continuous fiber processes include filament winding, wherein thefilament in the form of discrete strands or roving is coated with aresin, then wound on a mandrel at a predetermined angle and windingthickness to yield composite articles having high strength when theresin borne on the filament is cured.

In order to have commercial utility the polymeric resins employed infilament winding operations must exhibit low initial viscosity and longpot-life in the process systems in which they are employed. Lowviscosity is required in order that deposition of the resin on thefilament be highly uniform in character, as is required to achievesubstantially uniform properties in the final product article. Ifviscosity changes appreciably during the filament winding operation, theapplied resin thickness may change significantly, resulting in localizedstresses or discontinuities in the final product article, productarticles which are not within required dimensional tolerancespecifications, and inadequate curing of the resin. In addition, thetensional forces on the resin impregnated filaments being processed willsignificantly increase as the resin viscosity increases, to such extentthat the filament becomes highly susceptible to snapping, i.e.,tensionally breaking.

Long pot-life of the resin is particularly necessary infilament windingoperations where processing times may be on the order of hours. Sincethe resin is continuously being applied to the filament in theseprocesses, the resin bath or other source of the resin must becontinually replenished with resin coating material, and it is thereforenecessary that the resin not "set up" or gel in the source bath or othersource container and applicating means.

For example, in the fabrication of rocket motors, a resin-bearingfilament is wound onto a solid rocket fuel body. In such applications,since the filament winding operation may take upwards of 6 hours andsince viscosity must be substantially stable during this period, a longpot-life resin is essential, and consequently the filament wound bodymust be rotated until full cure of the resin is achieved, which in thecase of conventional epoxy resins can range from hours (for heat curedresins) to days (for resins cured at ambient temperatures). Continuousrotation of the mandrel and filament winding is essential in such cases,since cessation of rotation would result in the viscous resin saggingand dripping under gravitational forces, resulting in a resin-rich lowerportion of the product article and a resin-poor upper portion of theproduct. Accordingly, it is desirable to cure the fiber array quicklyonce it has been formed.

The difficulties inherent in balancing the properties of long pot-lifeand a quick and easily controlled cure have resulted in the developmentof numerous types of resins. And within each class of resin, attemptshave been made to vary the conditions under which the resins will cureeffectively. The standard resins which have been employed in continuousfilament processes, as well as in other systems of fiber/resin compositemanufacture, generally have deficiencies which have specifically limitedtheir utility in these processes.

The epoxy resins form an extremely important and versatile class ofresins. These resins exhibit excellent resistance to chemicals, willadhere to glass and a variety of other materials, show electricalinsulation properties, and are relatively easy to use. Among the epoxyresins, systems employing epoxy compounds in conjunction witholefinically unsaturated compounds have found wide acceptance in theart. In particular, resins comprising epoxies and acrylates have beenfound to be especially useful. This class of resins includes blends ofepoxies and acrylates ("epoxy/acrylate" resins) as well as compositionswherein the principal resin component is an acrylic acid-modified epoxywherein some or all of the epoxy groups have been consumed to produceunsaturated resins. Partially acrylated epoxies are occasionallyidentified as "dual-functional" compounds since they are designed toexhibit both epoxy and acrylate functional groups on the same molecule.

Within the aforementioned class of epoxy/acrylate systems, compositionshave been generated which are adapted to various cure conditions. Suchcompositions have employed heat curing mechanisms, actinic radiationcuring mechanisms, or a combination of both.

Heat curing alone has several disadvantages including reducing theviscosity of the resin, causing it to become more fluid and therebymaking it more difficult to handle the article, as well as moredifficult to achieve a product of isotropic character. In applicationssuch as filament winding, this drop in viscosity results in resin drip,as previously mentioned. Yet heat curing of epoxy/acrylate systems is aneffective and practical means of curing the resins to the fully hardenedstate that is the source of the resins' great utility.

Heat cured epoxy resin systems are disclosed by U.S. Pat. Nos. 3,408,422to May et al., 3,441,543 to Heilman, RE 27,973 (3,594,247) to Penningtonet al., 3,678,131 to Klapprott et al., 4,017,453 to Heilman et al.,4,025,578 to Siebert, 4,447,586 to Shimp, 4,515,737 to Karino et al.,and 5,011,721 to Decker et al.

Exemplary of heat cured compositions are the compositions of U.S. Pat.No. 3,408,422 to May et al. May et al. discloses compositions of anacrylated epoxy polymer and a hydroxylamine (as a stabilizer), as wellas unsaturated monomers and peroxides having decomposition temperaturesbelow 150° C. The compositions described by May et al. are heat cured,and include curing agents such as "onium" salts.

The use of actinic radiation to cure or partially cure, i.e., gel theresin, can substantially increase the viscosity of the resin on theformed article. Actinic radiation generally cannot induce completehardening of the resin and such systems usually employ a catalyst and/ora heat cure step to fully cure the resins. An example of such a processis U.S. Pat. No. 4,892,764 to Drain et al. which employs ultraviolet(UV) light induced polymerization, and requires additional curing atambient temperatures for extended periods. The Drain et al. patent alsoemploys an aliphatic diamine catalyst which significantly reduces thepot-life of the uncured resin. While the compositions of the Drain etal. patent exhibit some of the desirable resistance to the drip and sagof resin under the forces of gravity, this is due to the fact that theyare designed to be cured at room temperature. The Drain compositions arenot intended to be heat-cured and as a result exhibit low glasstransition temperatures (T_(g)), thereby having limited utility inapplications where the temperature resistance of the cured resins iscritical.

Other UV curing systems are found in U.S. Pat. No. 3,922,426 to Feltzindescribing filament wound articles impregnated with an ultraviolet lightcurable resin comprising an unsaturated polyester, an unsaturatedmonomer, an organic peroxide, and a photosensitizer. More specifically,Feltzin discloses organic peroxides with half-lives at temperaturesbetween 26° C. and 172° C. Other filament winding systems using UV orother actinic radiation to cure resins include U.S. Pat. Nos. 3,660,144,3,660,145 and 3,660,371 to Johnson et al., 3,772,062 to Shur et al., and4,479,984 to Levy et al.

Traditionally, dual-curing epoxy/acrylate systems, i.e., systems whichemploy both an initial actinic radiation exposure and a subsequentthermal polymerization step, have been used for numerous purposesincluding adhesives, coatings, and prepregs such as those involvingfilament winding. Such dual-curing prepreg compositions have employedblends of epoxies and acrylates, epoxy curing agents andphotoinitiators.

Dual-curing compositions of this kind are described in U.S. Pat. No.4,092,443 to Green. Green discloses dual-cured filament impregnatingresin compositions including a heat curable epoxide orepoxide-containing compound, a photopolymerizable component, such asacrylates, methacrylates and other polyolefinically unsaturatedcompounds. Heat activated curing agents such as amines, borontrihalides, imidazoles, and anhydrides, as well as optional use ofphotocatalysts, such as phenones and photo-activated organic peroxides,are also disclosed. The Green compositions, however suffer from a numberof the disadvantages associated with dual-cured systems. Principally,these compositions provide little or no resistance to resin drip duringthe heating step. Articles formed from the Green compositions andprocess therefore require rotation during heating in order to retainuniformity of resin distribution and the isotropic characteristics andproperties dependent thereon.

U.S. Pat. No. 3,937,855 to Gruenwald describes the impregnation ofinsulated electromagnetic coils with dual-curing resin compositions. Thepreferred compositions are polyesters solubilized in unsaturatedmonomers and mixed with peroxides activated by high temperatures alongwith accelerators such as a tertiary amine or an organo-cobalt compound.The resins described by the Gruenwald patent are quickly gelled byexposing the surface of the applied resin to a highly reactive chemicalcross-linking agent, i.e., organic peroxides such as methyl ethyl ketoneperoxide, cyclohexanone peroxide, diacetyl peroxide, dilauryl peroxide,cumyl hydroperoxide and benzoyl peroxide. Alternatively, the quickgelation of the resin at the periphery at ambient temperature can beaccomplished by incorporation of a photo activator such as a benzoinether and exposure of the resin to UV light.

U.S. Pat. No. 4,230,766 to Gaussens et al. discloses dual-curingcompositions of (meth)acrylated epoxy resins, unsaturated monomers,photoinitiators, and organic peroxides. The resins of the Gaussens etal. patent are cured first by ultraviolet light exposure and heatexposure as a second cure step. The peroxides disclosed by Gaussens etal. include lauroyl peroxide and benzoyl peroxide.

U.S. Pat. No. 3,935,330 to Smith et al. describes dual-curing resinsincluding polyepoxide monomers or polymers, urea/formaldehyde resins, ora melamine/formaldehyde resin, and a thermally curable cross-linker. Thecompositions described by Smith et al. may also include adual-functional (meth)acrylamide having at least one double bond and atleast one oxirane group. Another component of the compositions includesan ultraviolet light sensitive acrylate. Free radical initiators areincluded such as organic peroxides including di-t-butyl peroxide,benzoyl peroxide, t-butyl hydroperoxide, perbenzoic acid, and t-butylperacetic acid. Smith et al. also disclose photosensitizers includingphenones. The compositions disclosed by Smith et al. are described asbeing cured by an ultraviolet light exposure and are subsequentlyexposed to heat.

None of the aforementioned patents disclose dual-curing filament windingor prepreg resin compositions resistant to the resin sag and drip causedby heat curing. Other measures have generally been needed includingspraying a curing agent onto an uncured wound article, e.g., U.S. Pat.No. 3,937,855 to Gruenwald or, more commonly, requiring that the woundarticle be rotated during the heat cure.

Therefore, it would be a significant advance in the art to overcome theabove-described difficulties associated with filament winding processes,in a manner which would obviate the use of additional curing steps andlong rotation periods heretofore necessary to obtain quality compositeshaving uniform characteristics.

The present invention solves the disadvantages inherent in the prior artby providing compositions that maintain stable low pot-life viscositiesfor a significant period of time such that commercial filament windingprocesses are practicable. The compositions of the present inventionalso exhibit relatively high glass transition temperatures and areintended to be useful in high temperature applications. Unexpectedly,the resin compositions of the present invention allow uniform propertiesof the cured product to be obtained without drip or excessive flow ofthe resin during the heat-cure stage.

Accordingly, it is an object of the present invention to provide animproved process for forming fiber/resin composites.

It is a further object of the invention to provide an improved processfor filament winding which overcomes the above-described deficiencies ofthe prior art practice of these processes.

It is another object of the invention to provide filament wound articleswhich are readily and economically formed, and which are rapidlyprocessed for subsequent handling, packaging, or other processingoperations.

Other objects and advantages of the present invention will be more fullyapparent from the ensuing disclosure and appended claims.

SUMMARY OF THE INVENTION

In one aspect, the present invention relates to resin compositionsuseful for filament winding applications. The compositions include anepoxy component including at least one polyepoxide resin curable byheat, an olefinically unsaturated monomer component including at leastone polyolefinically unsaturated monomer curable by actinic radiation,at least one photoinitiator, at least one organic peroxide, and a heatactivated curing agent for epoxides. The compositions of the presentinvention have an initial viscosity less than about 2000 centipoise(cps), and are capable of retaining substantially the same viscosity forat least about 2 hours, and preferably about 4 to 8 hours, attemperatures ranging from about ambient temperature up to about 60° C.On being exposed to actinic radiation the compositions are capable ofbeing immobilized to a gelled state which will resist substantial resindrip during the heat cure process.

The resin compositions include an organic peroxide selected from thegroup of organic peroxides having 10 hour decomposition half lives attemperatures of from about 50° C. to less than about 104° C. Peroxidesoutside of the upper range have generally not been found to be effectiveat preventing resin drip. In general, useful peroxides include diacylperoxides, peroxydicarbonates, peroxyesters, and peroxyketals. Mixturesof peroxides are also contemplated.

Polyepoxide resins useful in the resins of the present invention may beselected from the classes consisting of polyglycidyl andpoly(β-methylglycidyl)ethers of dihydric and polyhydric alcohols andphenols, novolaks, alkyl-substituted phenols and halogen-substitutedphenols; poly(N-glycidyl) compounds obtained from amines containing atleast 2 amino-hydrogen atoms; triglycidylisocyanurate; N,N'-diglycidylderivatives of cyclic alkaline ureas and hydantoins; andpoly(S-glycidyl) derivatives of dithiols. Mixtures of these resins arealso useful.

The compositions of the present invention contain at least onepolyolefinically unsaturated monomer selected from the group consistingof acrylic and methacrylic resins, vinyl monomers, and unsaturatedpolyesters solubilized in vinyl monomers. The compositions may alsoinclude one or more mono-olefinically unsaturated monomers useful asdiluents.

Useful photoinitiators include benzophenone and substitutedbenzophenones, acetophenone and substituted acetophenones, benzoin andits alkyl ethers, xanthone and substituted xanthones, camphoroquinoneperoxyesters, and 9-fluorene carboxylic acid peroxyesters. Mixtures ofthese compounds may be employed.

The resins contain at least one heat activated curing agent. The curingagent may be an amine-containing compound or an anhydride. Whenamine-containing curing agents are employed they may be selected fromthe group consisting of dicyandiamides, boron trifluoride:aminecomplexes, boron trichloride:amine complexes, latent amine curatives,tertiary amines, aromatic polyamines, and imidazoles. Mixtures of curingagents are also contemplated. Alternatively, the resins may contain apolycarboxylic acid anhydride heat activated curing agent. The anhydridecuring agents are generally employed in combination with a minor amountof an amine-containing accelerator for increased cure speed. When theanhydride curing agent is used, the accelerator may also be selectedfrom the group consisting of dicyandiamides, boron trifluoride:aminecomplexes, boron trichloride:amine complexes, latent amine curatives,tertiary amines, aromatic polyamines, and imidazoles.

In another embodiment, the present invention includes a process forproducing fiber/resin composites comprising a fiber substrate and adual-cured resin composition. The resin composition will comprise atleast one polyepoxide resin curable by heat, at least onepolyolefinically unsaturated monomer which when subjected to sufficientactinic radiation immobilizes the polyepoxide resin, a photoinitiator,an organic peroxide having a 10 hour decomposition half life at atemperature of from about 50° C. to less than about 104° C., and atleast one heat activated curing agent for epoxides. In this process thefiber resin composite is initially cured by exposure to actinicradiation sufficient to immobilize the polyepoxide resin so that theresin exhibits no resin drip when subjected to a further heat cure step.

In another aspect, the present invention includes fiber/resin compositesformed by the process of applying a liquid resin, having a viscosity ofabout 2000 centipoise (cps) or less and a pot-life of at least 2 hours,and preferably 4 to 8 hours, at temperatures ranging from about ambienttemperature to about 60° C., to a fiber, subjecting the fiber/resincomposite to actinic radiation sufficient to permanently immobilize theresin, and then subjecting the fiber resin composite to heat sufficientto cure the resin. The resin composition comprises a heat curablepolyepoxide resin, an actinic radiation curable polyolefinicallyunsaturated monomer, a photoinitiator, an organic peroxide having a 10hour decomposition half life at a temperature of from about 50° C. toless than about 104° C. and a heat activated curing agent for epoxides.

DETAILED DESCRIPTION

Product articles according to the present invention may be made by anyof a wide variety of fiber/resin composite forming methods, includingthose utilized in forming fiber/resin matrices comprising discontinuousfibers. For example, lay-up techniques, sheet molding, resin transfermoldings, etc., as well as methods applicable to the use of continuousfilament, such as filament winding, braiding, and pultrusion may beused. Further, fiber/resin composite articles may be formed by acombination of these methods, such as where a solid rod is formed bypultrusion and subsequently used as the core body for filament winding.

In one preferred embodiment, the articles produced according to theinvention may comprise a filament array of substantially parallellyaligned, laterally continuous filaments which have been impregnated withthe resin compositions of the invention and subjected to actinicradiation curingly effective for the actinic radiation curable resincomponent of the composition.

As used herein, the term "laterally continuous", when used to describefilament arrays of parallelly aligned filaments, means that the adjacentfilaments in the parallelly aligned array have the resin compositionbetween their facing surfaces, without gross voids, spaces, ordiscontinuities therebetween. The resin composition possesses sufficientflow characteristics, as distinct from drip or sag, to uniformly bindadjacent filaments together.

In producing filament wound articles according to the present invention,wherein the filaments are treated, i.e., coated or impregnated, with theresin composition, the actinic radiation may be applied to the filamentprior to, simultaneously with, or subsequent to winding of the treatedfilament onto the substrate mandrel. Such concurrent actinic irradiationof the resin borne on the filament facilitates a high degree ofprocessing flexibility in the fabrication of such filament woundarticles. In this manner, winding of articles of substantially irregularshape is facilitated because irradiating impregnated fibers prior tosubstrate contact can impart sufficient adhesive and tack qualities tocause the fiber to adhere to the substrate and/or each other whilepassing over areas where slippage would normally occur. Thus, in someinstances, it may be advantageous to irradiate the impregnated filamentprior to its application by winding onto the substrate. Alternatively itmay be desirable to filament wind the mandrel, and subsequently toirradiate the wound article.

Similarly, in the pultrusion formation of filament articles according tothe present invention, an array of parallelly aligned filaments ispultruded through a die imparting a selected cross-sectional shapethereto, the filament having been impregnated with the resin compositionof the invention. The resulting shaped filament array is subjected tocuringly effective actinic radiation concurrently with its passagethrough the die. Such concurrent irradiation may be effected eitherprior to or subsequent to passage of the filament array through the die,insofar as the ultimate shape is imparted somewhat upstream of the diein proximity to the forming die openings. In a specific application, theparticular placement and operation of the actinic radiation source foreffectuating curing will be readily determinable by those skilled in theart without undue experimentation.

The use of UV light provides significant processing and handlingadvantages during manufacture by instantly immobilizing the resin.Immobilization of the resin is controlled to provide sufficient gelationto prevent flow out of the part but allow good wetting between layers,thus assuring even resin distribution, reduced void formation and easeof handling of the finished part without resin migration, sagging ordripping. The rapid gelation stage, in most cases, also eases handlingduring the heat-cure.

Advantages of the present invention include elimination of runs, drips,migration, and resin-rich/resin-poor areas; curing of the resin whileparts are stationary, i.e., no requirement for rotation; a process whichyields even resin distribution, reduced voids, lessens clean up andreduces resin usage and waste; and the low initial viscosity promotesexceptionally fast filling of parts and composite structures which canbe rapidly controlled by UV radiation.

The filament winding processes used with the present compositions arefor the most part continuous processes. Typically, the resin compositionis housed in an open vessel beneath a rotating roller. The rotatingroller is partially submerged in the resin so as to coat the roller asit rotates. Fiber is drawn from a spool and directed through the resinand into contact with the roller surface, whereby the fiber is coatedwith resin as it passes. Actinic radiation is directed at the coatedfiber as it leaves the roller, thereby gelling and immobilizing theresin. The gelled resin is wound on a mandrel, as previously described,and may be further cured, if desired or necessary, by actinic radiationprior to heat cure.

Subsequent to winding, the formed article is placed in an oven at anappropriate cure temperature. In general, the compositions or thepresent invention can substantially reach a fully cured state by heatcuring at about 150° C. to about 200° C. for about two to four hours. Itwill be appreciated by those skilled in the art that the time andtemperature of the heat cure may be varied to reach particular desiredresults.

The dual curing filament winding resins of the present invention areformulated with the aforementioned polyolefinically unsaturatedmonomers, and preferably polyacrylate monomers, that form a cross-linkedgel upon exposure to actinic radiation, and preferably UV light. Thiscross-linking prevents resin dripping from the part during the windingand during the heat cure. However, when certain fibers are employed thatscreen UV light, such as graphite or Kevlar, or when using high windingspeeds with most fibers, a portion of the acrylate can remain uncuredafter exposure to UV light. Thus, although the resin does not drip offthe part during filament winding, it may tend to drip during theheat-cure cycle unless appropriate measures are taken to reduce theflowability of the resin.

The degree of gelation of a given resin composition will largely dependon the amount and type of actinic radiation to which it is exposed.Exposure time is easily controllable, as is the intensity and type ofradiation. These parameters are easily determinable by one reasonablyskilled in the art, and may vary in accordance with the choice of resincomposition, fiber substrate and type of product desired. A singleactinic source, for example UV light, or alternatively multiple sourcesof light, may be focused on the resin coated fiber to effectuategelation. The winding speed can also be closely controlled, therebycontrolling the duration of exposure of the resin coated fiber to thebeam of radiation. In certain commercial applications, winding speeds ofabout 12 inches/second to about 20 inches/second are useful. Radiationintensities of, for example UV light, may be from about 120milliwatts/cm² to about 180 milliwatts/cm². These ranges are not in anyway intended to be limiting of the present invention, but are merelyillustrative of certain useful ranges. Other winding speeds andintensities of light may easily be chosen by those skilled in the art.

In addition, the dilution of the polyolefinically unsaturated portion ofthe composition by the unreacted epoxy system, and the increasedviscosity that occurs upon gelation, together can reduce the degree ofvinyl reaction relative to a 100 wt. % vinyl composition, furtherimpeding the thoroughness of the cross-linking and reducing the resin'scapacity to resist dripping when heated.

The inclusion of a thermally activated radical source, i.e., a peroxide,will tend to increase the extent of the vinyl reaction as thecomposition is heated. One effect of a more complete vinyl reaction isto compensate for the decreased viscosity that occurs as the compositionheats up to the heat cure onset temperature of the major components(usually a heat-curing epoxy system). Another effect is to compensatefor possible inadequacies in the geometry of the actinic cure step whereexposure of the resin is not optimal. The peroxide enables the furtherextension of the gelation of the resin to any portions of the resinwhich are less fully exposed to the actinic source. The intent is toretain a tacky, relatively soft gel during the application stage, so asto improve adhesion and facilitate handling during fabrication, while atthe same time producing a composition which will not drip during thecuring heat-up stage.

While not wishing to be bound by any one theory, applicants believe thatthe peroxide plays a role in the reaction of unreacted vinyl groupstrapped in the epoxy resin diluted gel formed during the irradiationstage. Normally, it would be expected that these groups might thermallypolymerize during the final high temperature epoxy cure. It is possible,however, that the more extensive vinyl polymerization at a lowertemperature, produced by initiation using a suitable peroxide, leads toa stronger structure when the anhydride-hydroxyl reaction takes over inthe case of the anhydride curing compositions. Alternatively, theperoxide may be producing direct vinyl bonding to the cured epoxy byabstraction on epoxy compounds followed by vinyl addition to the newradical sites.

As was discussed above, the resin component of partially cured filamentwound articles will tend to drip upon heating, generally requiring therotation of the articles during heat curing to avoid anisotropies. Forexample, amine curing resin formulations, in accordance with the presentinvention but containing no peroxide, were used to form compositearticles as described elsewhere herein. Articles were formed by filamentwinding onto mandrels to which thermocouples had been attached, and therise in temperature of the article during heat cure was then correlatedwith the onset of resin drip.

It was observed that the onset of the drip of the amine curing resins ofthe present invention will occur, in the absence of peroxide, generallyin the range of from about 80° C. to about 100° C., depending upon thecomposition of the resin. The peroxide chosen for use in any particularresin formulation will therefore depend in part on the resin drip onsettemperature of the formulation. To be useful for the present invention,the peroxide selected must provide sufficient additional cross-linkingof the gel to offset any decrease in resin viscosity that wouldotherwise occur during the heat-up process. In addition, for the benefitof the peroxide to be obtained, the offsetting cross-linking induced bythe thermally activated peroxide must occur at a temperature below ornear the temperature at which the drip phenomenon begins. Because thedecomposition of each peroxide is expressed as a ten hour half-lifefunction of temperature, a peroxide will begin to decompose attemperatures below its ten hour half-life temperature (T_(1/2)). Theperoxide can therefore begin to cross-link the gelled resin before thetemperature rises sufficiently to otherwise cause the resin to drip. Ingeneral, the peroxides useful in the present invention will have aT_(1/2) less than about 104° C. Peroxides having T_(1/2) 's of about104° C. or greater generally have not been found to be useful in theresins of the invention. It is believed that such peroxides do notgenerate sufficient cross-linking of the gel until after resin drip hasbegun during the heat-up process.

Thus, a range of dual-curing epoxy/polyolefinically unsaturatedformulations has been developed. These compositions are designed to forma soft gel which allows for interlayer wetting when exposed to UVradiation. The compositions are further designed to retain theirnon-flow properties during the heat-up stage of heat-curing by producingadditional immobilizing cross-linking during the heat-up. This isaccomplished by means of a thermally activated radical source in theformulation, namely the class of peroxides described herein.

A peroxide, which decomposes on heating to form radicals is added to theformulation to initiate the polymerization of any unreactedpolyolefinically unsaturated monomer. The choice of peroxide is criticalto prevent dripping during heat-cure. The peroxide must possess a 10hour half-life decomposition temperature of less than 104° C. A peroxidewith a higher value decomposes too slowly and the polyolefin does notpolymerize sufficiently to prevent dripping during the heat-cure.

A preferred class of compositions of the present invention are the"amine curing resins". These amine curing resins are created by mixingan epoxy resin component comprising at least one polyepoxide, apolyolefinic component including at least one polyacrylate, aphotoinitiator and a peroxide, with a curing component comprising anamine-containing heat activated curing agent. Separately, the twocomponents (epoxy component and curing component) of the amine curingresins have essentially unlimited shelf life. When mixed, thecompositions can retain a usable viscosity (pot-life) i.e., less thanabout 2000 centipoise (cps), for a minimum of about 2 and preferablyabout 4 to 8 hours at temperatures ranging from about ambienttemperature to about 60° C. The amine curing resin compositions have aT_(g) in the range of about 110° C. to about 160° C. when fully cured.

The amine curing resins of the present invention have an epoxy componentpresent in an amount ranging from about 60 wt. % to about 85 wt. %, andpreferably, about 63 wt. % to about 75 wt. %; a polyolefinic componentpresent in an amount ranging from about 5 wt. % to about 30 wt. %, andpreferably from about 10 wt. % to about 20 wt. % of the composition.Most preferably the polyolefin component is present at about 15 wt. % ofthe composition. The amine-containing heat activated curing agent isgenerally present in an amount ranging from about 2 wt. % to about 10wt. %, and preferably from about 3 wt. % to about 6 wt. %. Mostpreferably the heat activated curing agent is present in an amount ofabout 5.5 wt. %. The photoinitiator is generally present in an amountranging from about 1 wt. % to about 10 wt. %, and most preferably fromabout 2 wt. % to about 5 wt. %. The free radical initiator (organicperoxide) is present in an amount ranging from about 0.2 wt. % to about2 wt. %, preferably from about 0.5 wt. % to about 1.5 wt. %.Miscellaneous additives such as wetting and defoaming agents can beadded collectively in amounts of about 0.5 to about 1% by weight of thecomposition, added as part of the resin component. Optionally, fireretardant materials such as phosphorous-containing compounds may bepresent in amounts of about 2% to about 10%, and preferably about 3% toabout 5% by weight of the composition.

Another preferred class of compositions of the present invention are the"anhydride curing resins". These compositions comprise a mixture of anepoxy resin component including at least one polyepoxide, a polyolefiniccomponent including at least one polyacrylate, a photoinitiator, and aperoxide, with a curing component comprising a carboxylic acid anhydrideand an anhydride accelerator. The anhydride curing compositions exhibita T_(g) of from about 110° C. to about 160° C. when fully cured. Theanhydride curing compositions also generally exhibit lower viscositiesthan the amine curing resins of the present invention. Because thereaction between the epoxy and the anhydride is inherently slower thanwith amine curing agent, the anhydride curing resins have a greaterpot-life capability, e.g., at least a 24 hour pot-life.

In the anhydride curing compositions of the present invention, the epoxycomponent may be present in amounts ranging from about 37 wt. % to about48 wt. % of the composition, most preferably from about 40 wt. % toabout 45 wt. % of the composition. The anhydride component may bepresent in amounts ranging from about 33 wt. % to about 43 wt. %, mostpreferably from about 36 wt. % to about 41 wt. % of the composition. Theanhydride accelerator may be present in an amount of about 0.1 wt. % toabout 5.0 wt. %; preferably in an amount of about 1.0 wt. % to about 2.0wt. %. The polyolefinic component may be present in an amount rangingfrom about 10 wt. % to about 30 wt. %, preferably from about 10 wt. % toabout 20 wt. % and most preferably about 12 wt. % to about 15 wt. %. Thephotoinitiator is present in an amount ranging from about 1 wt. % toabout 10 wt. %, and preferably from about 1.5 wt. % to about 5 wt. %.The free radical initiator (organic peroxide) may be present in amountsranging from about 0.2 wt. % to about 2 wt. %, and preferably from about0.3 wt. % to about 1 wt. %. Miscellaneous additives such as wetting anddefoaming agents can be added collectively in amounts of about 0.5 toabout 1% by weight of the composition, added as part of the resincomponent. Optionally, fire retardant materials such asphosphorous-containing compounds may be present in amounts of about 2%to about 10%, and preferably about 3% to about 5% by weight of thecomposition.

Epoxy resins useful in the compositions of the present invention includepolyepoxides curable by elevated temperature. Examples of thesepolyepoxides include polyglycidyl and poly(β-methylglycidyl) ethersobtainable by reaction of a compound containing at least two freealcoholic hydroxyl and/or phenolic hydroxyl groups per molecule with theappropriate epichlorohydrin under alkaline conditions or, alternatively,in the presence of an acidic catalyst and subsequent treatment withalkali. These ethers may be made from acyclic alcohols such as ethyleneglycol, diethylene glycol, and higher poly(oxyethylene) glycols,propane-1,2-diol and poly(oxypropylene) glycols, propane-1,3-diol,butane-1,4-diol, poly(oxytetramethylene) glycols, pentane-1,5-diol,hexane-2,4,6-triol, glycerol, 1,1,1-trimethylolpropane, pentaerythritol,sorbitol, and poly(epichlorohydrin); from cycloaliphatic alcohols suchas resorcinol, quinitol, bis(4-hydroxycyclohexyl)methane,2,2-bis(4-hydroxycyclohexyl)propane, and1,1-bis(hydroxymethyl)-cyclohex-3-ene; and from alcohols having aromaticnuclei, such as N,N-bis(2-hydroxyethyl)aniline andp,p'-bis(2-hydroxyethylamino)diphenylmethane. Or they may be made frommononuclear phenols, such as resorcinol and hydroquinone, and frompolynuclear phenols, such as bis(4-hydroxyphenyl)methane,4,4'-dihydroxydiphenyl, bis(4-hydroxyphenyl)sulphone,1,1,2,2-tetrabis(4-hydroxyphenyl)ethane,2,2,-bis(4-hydroxyphenyl)propane (otherwise known as bisphenol A),2,2-bis(3,5-dibromo-4-hydroxyphenyl)propane, and novolaks formed fromaldehydes such as formaldehyde, acetaldehyde, chloral, andfurfuraldehyde, with phenols such as phenol itself, and phenolssubstituted in the ring by chlorine atoms or by alkyl groups eachcontaining up to nine carbon atoms, such as 4-chlorophenol,2-methylphenol, and 4-t-butylphenol.

Poly(N-glycidyl) compounds include, for example, those obtained bydehydrochlorination of the reaction products of epichlorohydrin withamines containing at least two amino-hydrogen atoms, such as aniline,n-butylamine, bis(4-aminophenyl)methane, andbis(4-methylaminophenyl)methane; triglycidyl isocyanurate; andN,N'-diglycidyl derivatives of cyclic alkylene ureas, such asethyleneurea and 1,3-propyleneureas, and of hydantoins such as5,5-dimethylhydantoin.

Epoxide resins having the 1,2-epoxide groups attached to different kindsof hetero atoms may be employed, e.g., the N,N,O-triglycidyl derivativeof 4-aminophenol, the glycidyl ether-glycidyl ester of salicylic acid,N-glycidyl-N'-(2-glycidyloxy-propyl)-5,5-dimethylhydantoin, and2-glycydyloxy-1,3-bis(5,5-dimethyl-1-glycidylhydantoin-3-yl)propane.

Such epoxies are available from a variety of commercial sources, such asthe EPON series from Shell Chemical Co., the EPI-REZ series fromRhone-Poulenc, the Araldite series from Ciba-Geigy, the D.E.R. seriesfrom Dow Chemical Co., and the EPOTUF series from Reichhold.

Also useful are halogenated epoxy resins such as the brominated epoxidesavailable from the sources shown above. Halogenated epoxy resins incombination with other fire retardant materials may be suitable for useas fire retardant additives in the compositions of the presentinvention.

Especially preferred epoxy resins useful in the present invention arethe diglycidyl ethers of bisphenol A marketed under the tradenames EPON825 and EPON 828 available from Shell Chemical Co., D.E.R. 331 and 332available from Dow Chemical Co., and the cycloaliphatic epoxy resinmarketed as ERL-4221 by Union Carbide Co.

Various epoxies such as the glycidyl ethers marketed as the EPODILseries by Pacific Anchor Chemical Corporation, a division of AirProducts and Chemicals Inc., may be added as epoxy diluents, to reducethe viscosities of the resins of the present invention.

It will be understood that the foregoing list of epoxy compounds isintended only to be illustrative in character, and that other compoundshaving 1,2 epoxide functionality and curable by heat may potentially beemployed. Other optional epoxy compounds may be present which have bothepoxy functionality and olefinically unsaturated functionality("dual-functional" resins).

Suitable polyolefinically unsaturated components of the compositions mayinclude poly(meth)acrylic resins, polyvinyl monomers, andpolyunsaturated polyesters solubilized in vinyl monomers. As usedherein, the term "(meth)acrylic" is intended to be broadly construed toinclude acrylic as well as methacrylic compounds, e.g., acrylic estersand methacrylic esters.

It is preferred that the polyolefinically unsaturated monomer have a lowviscosity to offset the effect of any higher viscosity component so asto retain the low composition viscosity required for effective filamentwinding. In addition, the polyolefinically unsaturated monomer componentmay comprise one or more low viscosity monoolefinically unsaturatedmonomers as diluents, but in any event, the olefinically unsaturatedmonomer component must comprise at least one polyolefinicallyunsaturated monomer. As used herein "polyolefinically unsaturated" meanshaving at least two olefinic double bonds. The polyolefinicallyunsaturated monomers may be used in amounts of about 5% to about 30% andpreferably about 10% to 20% by weight of the composition.

Polyacrylates are generally useful, including 1,3-butylene glycoldiacrylate, diethylene glycol diacrylate, 1,6-hexanediol diacrylate,neopentylglycol diacrylate, polyethylene glycol diacrylate,tetraethylene glycol diacrylate, methylene glycol diacrylate,pentaerythritol tetraacrylate, tripropylene glycol diacrylate,ethoxylated bisphenol-A-diacrylate, trimethylolpropane triacrylate,di-trimethylolopropane tetraacrylate, dipenterythritol pentaacrylate,pentaerythritol triacrylate and the corresponding methacrylatecompounds. Also useful are reaction products of (meth)acrylic acid andepoxide resins, and urethane resins. Suitable poly(meth)acrylic estercompounds are also described in U.S. Pat. Nos. 4,051,195, 2,895,950,3,218,305, and 3,425,988.

Useful (meth)acrylic resins include esters and amides of (meth)acrylicacid as well as comonomers thereof with other copolymerizable monomers.Illustrative esters include methyl acrylate, methyl methacrylate,hydroxy ethyl acrylate, butyl methacrylate, octyl acrylate, and 2-epoxyethyl acrylate. Illustrative amides include bytoxymethyl acrylamide,methoacrylamide, and t-butyl acrylamide. Also suitable are copolymers ofsuch compounds, and copolymers with other monomers containingpolymerizable vinyl groups.

Another class of resins which are actinic radiation curable andpotentially,suitable for use in the compositions in the inventioninclude vinyl monomers such as styrene, vinyl toluene, vinylpyrrolidone, vinyl acetate, divinyl benzene, and the like.

A further useful class of actinic radiation curable resin materialscomprises unsaturated polyesters, solubilized in vinyl monomers, asordinarily prepared from alpha-beta ethylenically unsaturatedpolycarboxylic acids and polyhydric alcohols, as described for examplein U.S. Pat. No. 4,025,407.

Particularly preferred polyolefinically unsaturated components includetrimethylolopropane trimethacrylate, trimethylolpropane triacrylate,dipentaerythritol pentaacrylate, pentaerythritol triacrylate,ethoxylated trimethylolpropane triacrylate, 1,6 hexanediol diacrylate,neopentyl glycol diacrylate, pentaerythritol tetraacrylate, and 1,3butylene glycol diacrylate. Preferred monoacrylates includecyclohexylacrylate, 2-ethoxyethyl acrylate, 2-methoxyethyl acrylate,benzoyl acrylate, and isobornylacrylate. Such compounds are availablefrom a variety of sources. For example, a preferred polyacrylate,dipentaerythritol monohydroxypentaacrylate is available as SR 399 fromSartomer Co.

It will be understood by those skilled in the art that the foregoinglisting of polyolefinically unsaturated compounds is intended only to beillustrative in character, and that any other resin compounds havingsuch functionality in their molecules and curable under actinicradiation conditions may potentially be employed. In addition to thosemonomers required to be present, other optional monomers may be presentwhich have both acrylate and epoxy functionality ("dual-functional"monomers).

As used herein, "actinic radiation" means electromagnetic radiationhaving a wavelength of about 700 nm or less which is capable, directlyor indirectly, of curing the specified resin component of the resincomposition. By indirect curing in this context is meant curing undersuch electromagnetic radiation conditions, as initiated, promoted, orotherwise mediated by another compound.

Accordingly, a photoinitiator may be added to the composition in anamount effective to respond to the actinic radiation and to initiate andinduce curing of the associated resin, via substantial polymerizationthereof.

Suitable photoinitiators useful with ultraviolet (UV) actinic radiationcuring mono- and polyolefinic monomers include free radical generatingUV initiators such as benzophenone and substituted benzophenones,acetophenone and substituted acetophenones, benzoin and its alkyl estersand xanthone and substituted xanthones. Preferred photoinitiatorsinclude diethoxy-acetophenone, benzoin methyl ether, benzoin ethylether, benzoin isopropyl ether, diethoxyxanthone, chloro-thio-xanthone,azo-bisisobutyronitrile, N-methyl diethanol-amine-benzophenone andmixtures thereof.

Visible light initiators include camphoroquinone peroxyester initiatorsand 9-fluorene carboxylic acid peroxyesters.

Particularly preferred photoinitiators include2-hydroxy-2-methyl-1-phenyl-propan-1-one available as Darocur 1173 fromEM Industries, Inc., and2-benzyl-2-(dimethylamino)-1-[4-(4-morpholinyl)phenyl]-1-butanoneavailable as Irgacure 369 from Ciba-Geigy.

The present invention requires the use of organic peroxides having 10hour decomposition half-lives (10 hr. T_(1/2)) at temperatures of fromabout 50° C. to less than about 104° C. Peroxides having 10 hourdecomposition half-lives at temperatures below this range do not yieldcompositions which have stable pot-life and shelf-life characteristics.Peroxides having 10 hour decomposition half-lives at temperatures abovethis range have not been found to be effective in preventing resin dripduring the heat cure stage.

These peroxides include various diacylperoxides such as diisononanoylperoxide, decanoyl peroxide, lauroyl peroxide, succinic acid peroxideand benzoyl peroxide.

Also useful are various peroxydicarbonates such as di(n-propyl)peroxydicarbonate, di(sec-butyl)peroxydicarbonate, anddi(2-ethylhexyl)peroxydicarbonate.

Further useful peroxides include various peroxyesters such asα-cumylperoxyneodecanoate,1,1-dimethyl-3-hydroxy-butylperoxyneoheptanoate,α-cumylperoxyneoheptanoate, t-amyl-peroxyneodecanoate,t-butylperoxyneodecanoate, t-amyl-peroxypivalate, t-butylperoxypivalate,1-1-dimethyl-3-hydroxy-butylperoxy-2-ethylhexanoate,2,5-dimethyl-2,5-di(2-ethyl-hexanoylperoxy)hexane,t-amylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate,t-butylperoxyisobutyrate, t-butylperoxymaleic acid,t-butylperoxyacetate, t-amylperoxyacetate, t-amylperoxybenzoate,OO-t-butyl-O-isopropylmonoperoxycarbonate,2,5-dimethyl-2,5-di(benzoylperoxy)hexane,OO-t-butyl-O-(2-ethylhexyl)monoperoxycarbonate,OO-t-amyl-O-(2-ethylhexyl)monoperoxycarbonate.

In addition, certain peroxyketals are useful in the present inventionincluding 1,1-di(t-butylperoxy)-3,3,5-trimethyl cyclohexane,1,1-di(t-butylperoxy)cyclohexane, and 1,1-di(t-amylperoxy)cyclohexane.

Preferred organic peroxides include lauroyl peroxide, having a 10 hr.T_(1/2) of 64° C.; t-amylperoxy-2-ethylhexanoate, having a 10 hr.T_(1/2) of 75° C.; and 1,1-di(t-butylperoxy)-3,3,5-trimethylhexanehaving a 10 hr. T_(1/2) of 96° C. Lauroyl peroxide is available asAlperox-F; t-amylperoxy-2-ethylhexanoate is available as Lupersol 575;and 1,1-di(t-butylperoxy)-2,2,5-trimethylhexane is available as Lupersol256; all available from Elf Atochem North America, Inc.

Various conventional heat-activated curing agents for epoxies are usefulin the present invention including imidazoles, preferably2-ethyl-4-methyl imidazole,1-(2-cyanomethyl)-2-ethyl-α-4-methylimidazole and2-phenyl-4,5-dihydroxymethyl imidazole; aliphatic cycloaliphatic amines,preferably 2,2'-dimethyl-4,4'-methylene-bis(cyclohexylamine) (Ancamine2049); aromatic amines, preferably 4,4'-diaminodiphenyl sulfone(Ancamine S and Ancamine SP); a blend of aromatic and aliphatic amines(Ancamine 2038); Lewis Acid catalysts such as boron trifluoride:aminecomplexes, preferably BF₃ : benzyl amine (Anchor 1907), BF₃ :monoethylamine (Anchor 1948) and liquid BF₃ :amine complex (Anchor 1222); LewisBase catalysts such as t-amines, preferablytris(dimethylaminomethyl)phenol (Ancamine K. 54), dimethylaminomethylphenol (Ancamine 1110); dicyandiamides, preferably dicyandiamide(Amicure CG). The Ancamine, Anchor, and Amicure series are tradenamesfor heat activated curing agents marketed by Pacific Anchor PerformanceChemicals Division of Air Products and Chemicals, Inc.

Especially pertinent to the anhydride resin compositions of the presentinvention are the acid anhydride epoxy curing agents. These include,preferably, methyltetrahydrophthalic anhydride, methylhexahydrophthalicanhydride, chlorendic anhydride, and nadic methyl anhydride and mixturesthereof. Nadic methyl anhydride is available as AC-methyl fromAnhydrides and Chemicals, Inc.

It will be noted that anhydride based catalysis of epoxy polymerizationis an inherently slow process. Accordingly, the resin compositions ofthe present invention generally employ a minor amount of amineaccelerators of the anhydride catalysis, preferably benzyldimethylamine; 2-ethyl-4-methyl imidazole, available as Imicure EMI-24from Pacific Anchor; and2,4-diamino-6[2'-methylimidazolyl-(1)']ethyl-s-triazine isocyanurateadduct.

Other additives conventionally used in the art which do notsubstantially interfere with the objectives of the present invention maybe useful. Fillers, diluents, pigments, dyes, surface active agents,flame retardants and the like may be employed for their intendedpurposes.

The procedure for making the amine curing resin compositions of thepresent invention may be generally described as follows: the epoxide,polyolefin, photoinitiator, and miscellaneous additives such asdefoaming agents, wetting agents and, optionally, fire retardants areblended together to obtain a homogeneous mixture. Peroxide is added andthe mixture is further stirred. The resin component and a heat activatedcuring agent such as ethylmethyl imidazole are then mixed in aproportion of about 17 parts of resin component to 1 part of the curingagent, stirred and deaerated under vacuum. The mixture is then ready forfilament winding or preparation of prepreg.

The procedure for making the anhydride compositions of the presentinvention may be generally described as follows: the resin component ismade by mixing the epoxide, polyolefin, photoinitiator, and additionalmiscellaneous components, such as defoaming agents, wetting agents and,optionally, fire retardants. This blend is stirred until the solution ishomogeneous, e.g., approximately 10 minutes. A peroxide is added and themixture is further stirred, e.g., for an additional 10 minutes. Theanhydride component comprises a mixture of an anhydride, such as nadicmethyl anhydride, and an anhydride accelerator, such asbenzyldimethylamine. This mixture is stirred until homogeneous,approximately 10 minutes. The resin and anhydride components are thenmixed in a proportion of about 1.6 parts of the resin component to 1part of the anhydride component. The mixture is then further stirred anddeaerated under vacuum. The composition is then ready for filamentwinding or for preparation of prepreg.

Consolidation of the adjacent layers into a unitary structure requiressufficient flow of the gelled resin during the heat-cure stage to meldthe adjacent filaments into an integral whole and produce a qualitypart. In cases where excessive UV exposure has been applied in anattempt to alleviate subsequent dripping, the acrylate matrix is toorigid to allow such flow to occur. On the other hand, if the acrylate isinsufficiently exposed to actinic radiation so as to create too soft agel, dripping during the heat-cure stage is inevitable. Theimmobilization of the resin by actinic radiation must produce alattice-like matrix that has sufficient gel structure to preventdripping, but enough flowable character to allow the merger of therespective layers into a unitary mass, during the heat cure stage.

The following non-limiting examples are intended to further illustratethe present invention. Unless otherwise noted, amounts are given inweight percent of the total composition. Viscosities were determined bymeasuring 75 gram samples in a Brookfield DV I viscometer, using a 25°C. water bath.

EXAMPLE 1

Amine curing resin compositions (Compositions 1-4 set forth in Table Ibelow) were produced in accordance with the procedures of the presentinvention.

Filament wound articles were produced from the compositions using thegeneral methods described above. In particular, for Compositions 1-4,articles were produced using varying intensities and locations ofactinic light and varying winding speeds. Products were made using glassfiber and using carbon fiber.

Glass fiber articles were produced using two different winding speeds;12 inches/sec. and 20 inches/sec. At each speed, articles were producedwhich were exposed to one actinic radiation source, producing 120mW/cm², focused on the mandrel onto which the fiber was wound. Articleswere also produced, at each winding speed, which were exposed to tworadiation sources. The first exposure was to a 180 mW/cm² source as thefiber emerged from the resin bath. The second source was the 120 mW/cm²source at the mandrel as the fiber was wound. After winding, thesevarious articles were heat cured in an oven at 150° C. for two hours.Regardless of the winding speed and the number and location of actinicsources, the resins of the present invention exhibited no drip upon heatcure. Drip was assessed by collecting resin falling from the woundarticle onto a collector positioned beneath the article.

Carbon fiber articles were produced in similar fashion, using one or twoactinic sources. However, the intensities of the actinic radiation weregreater for the relatively UV-opaque carbon fiber windings than for therelatively UV-transmissive glass fiber windings. Specifically, thesource directed to the fiber on emerging from the resin bath was 450mW/cm² and the source focused on the mandrel was 250 mW/cm². Carbonfiber articles were produced at only one winding speed, i.e., 4inches/sec. Again, the articles were heat cured at 150° C. for twohours. Drip was observed in only one case, i.e., Composition 4.

As is evident from Table I, Compositions 1-4 are substantially identicalexcept for the particular peroxide used. It is apparent from the dripdata that the peroxides having a 10 hour T_(1/2) of less than 104° C.enable compositions which do not drip on heat-curing regardless of thefiber being used. Composition 4, employing t-butylperbenzoate with a 10hour T_(1/2) of 104° C., is useful on glass fiber, but is less desirablewhen applied to carbon fiber, as evidenced by observable drip.

                                      TABLE I                                     __________________________________________________________________________    AMINE CURING RESINS                                                                                      1    2   3   4                                                                wt. %                                                                              wt. %                                                                             wt. %                                                                             wt. %                                 __________________________________________________________________________    PART A                                                                        DIGLYCIDYL ETHER OF BISPHENOL A*                                                                         75   75  75  74.8                                  NEOPENTYLGLYCOL DIACRYLATE 15   15  15  14.7                                  HYDROXYMETHYLPHENYL PROPANONE                                                                            3    3   3   2.9                                   LAUROYL PEROXIDE (64° C.)                                                                         0.8  --  --  --                                    T-AMYLPEROXY-2-ETHYL-HEXANOATE (75° C.)                                                           --   0.8 --  --                                    DI(t-BUTYLPEROXY) TTHYL-   --   --  0.8 --                                    CYCLOHEXANE (96° C.)                                                   T-BUTYL PERBENZOATE (104° C.)                                                                     --   --  --  1.6                                   DEFOAMING AGENT*           0.5  0.5 0.5 0.5                                   WETTING AGENT*             0.1  0.1 0.1 0.1                                   PART B                                                                        ETHYL METHYL IMIDAZOLE     5.6  5.6 5.6 5.4                                   VISCOSITY (cps)                                                               0 HOUR                     730  860 1100                                                                              950                                   2 HOURS                    1050 --  --  --                                    4 HOURS                    SOLID                                                                              --  --  --                                    8 HOURS                    SOLID                                                                              1690                                                                              1860                                                                              2030                                  DRIP ON HOOP WIND                                                             GLASS FIBER                NO   NO  NO  NO                                    CARBON FIBER               NO   NO  NO  YES                                   __________________________________________________________________________     *The diglycidyl ether of Bisphenol A used in this example was EPON 825,       available from Shell Chemical Co. The defoaming agent employed in the         various examples throughout this specification is a mixture of foam           destroying polymers and polysiloxanes. The wetting agent employed in the      examples herein is a fluorinated surfactant.                             

EXAMPLE 2

Anhydride curing resin compositions (Compositions 5-8 set forth in TableII below) were produced in accordance with the procedures of the presentinvention. As in Example 1 above, articles were made using glass andcarbon fibers coated with the anhydride curing resins. Glass fiberarticles were wound at 12 inches/sec. and at 20 inches/sec., and at eachwinding speed, articles were made using single and double irradiationsat the intensities as described in Example 1. Upon heat cure none of theresins were observed to drip.

Carbon fiber articles were also formed at a winding speed of 4inches/sec. using both single and double exposures to actinic radiation.The intensities of the UV light source were 450 mW/cm² on the fiber onemerging from the resin bath, and 250 mW/cm² on the fiber as it waswound on the mandrel. No drip was observed upon heat cure except forcarbon fiber articles made using Composition 8, in which the peroxidewas t-butyl perbenzoate.

As is evident from Table II, Compositions 5-8 are substantiallyidentical except for the particular peroxide used. As with the aminecuring resin compositions described above in Table I, it is apparentfrom the drip data that peroxides having a 10 hour T_(1/2) of less than104° C. enable anhydride curing compositions to be formulated which donot drip on heat-curing. As was the case in Example 1 above, Composition8, a resin containing t-butylperbenzoate, when applied to UV-opaquecarbon fiber, dripped during heat cure.

                                      TABLE II                                    __________________________________________________________________________    ANHYDRIDE CURING RESINS                                                                               5   6   7   8                                                                 wt. %                                                                             wt. %                                                                             wt. %                                                                             wt. %                                     __________________________________________________________________________    PART A                                                                        DIGLYCIDYL ETHER OF BISPHENOL A                                                                       42.9                                                                              42.9                                                                              42.942.9                                                                          42.8                                      TMPTMA*                 14.5                                                                              14.5                                                                              14.5                                                                              14.4                                      HYDROXYMETHYLPHENYL PROPANONE                                                                         2.2 2.2 2.2 2.1                                       LAUROYL PEROXIDE (64° C.)**                                                                    0.4 --  --  --                                        T-AMYLPEROXY-2-ETHYL-   --  0.4 --  --                                        HEXANOATE (75° C.)**                                                   DI(t-BUTYOXY)           --  --  0.4 --                                        TRIMETHYLCYCLOHEXANE (96° C.)**                                        T-BUTYL PERBENZOATE (104° C.)**                                                                --  --  --  0.8                                       DEFOAMING AGENT         0.6 0.6 0.6 0.6                                       WETTING AGENT           0.1 0.1 0.1 0.1                                       PART B                                                                        NADIC METHYL ANHYDRIDE  38.7                                                                              38.7                                                                              38.7                                                                              38.6                                      BENZYL DIMETHYL AMINE   0.6 0.6 0.6 0.6                                       VISCOSITY (cps)                                                               0 HOUR                  650 1086                                                                              750 800                                       24 HOURS                1700                                                                              1416                                                                              1700                                                                              2100                                      48 HOURS                1700                                                                              2846                                                                              2000                                                                              2300                                      DRIP ON HOOP WIND                                                             GLASS FIBER             NO  NO  NO  NO                                        CARBON FIBER            NO  NO  NO  YES                                       __________________________________________________________________________     *TMPTMA is an abbreviation for trimethylolpropane trimethacrylate.            *Indicates 10 hour T.sub.1/2 temperature.                                

EXAMPLE 3

Resin compositions formulated in accordance with the procedures setforth herein are described in Table III. Composition 9 is representativeof an amine curing resin of the present invention. Composition 10 isrepresentative of Example 2 of U.S. Pat. No. 4,092,443 to Green.Composition 11 is representative of the amine curing resin of thepresent invention, but without an organic peroxide.

                  TABLE III                                                       ______________________________________                                                                9      10     11                                                              wt.    wt.    wt.                                     MATERIALS               %      %      %                                       ______________________________________                                        2,2-BIS(GLYCIDYLOXYPHENYL)                                                                            --     47.2   --                                      PROPANE*                                                                      DIGLYCIDYLETHER OF      74.4   --     75.5                                    BISPHENOL A**                                                                 ETHYL METHYL IMIDAZOLE  5.6    --     5.7                                     DICYANDIAMIDE           --     3.7    --                                      NEOPENTYL GLYCOL DIACRYLATE                                                                           14.9   47.2   15.1                                    T-AMYLPEROXY-2-ETHYLHEXANOATE                                                                         1.5    --     --                                      HYDROXYMETHYLPHENYL     3      --     3.1                                     PROPANONE                                                                     BENZYL DIMETHYL ACETAL  --     1.9    --                                      DEFOAMING AGENT         0.5    --     0.5                                     WETTING AGENT           0.1    --     0.1                                     ______________________________________                                         *EPON 828 from Dow Chemical Co.                                               **EPON 825 from Dow Chemical Co.                                         

The compositions were then used in a filament winding process inaccordance with the procedures described herein. These results aretabulated in Table IV, below. This process was conducted using fibersmade from glass and graphite, respectively, with each composition beingapplied to each kind of fiber in separate preparations. In addition, asfor previous Examples, two winding speeds were examined; 12 inches/sec.and 20 inches/sec. The coated fibers were first gelled by exposure to UVlight at an intensity of 120 mW/cm² as they were wound around a mandrel,and then placed in an oven for heat curing for 2 hours at a temperatureof 150° C. The resin was then observed for evidence of dripping and forquality of part consolidation (Table IV). Contrary to customary practicefor dual-curing filament processes, no rotation of the parts in the ovenwas performed. Rotation is conventionally required to compensate forexcessive resin flow during heating which creates drip and non- uniformdistribution of the resin on the fiber substrate.

                                      TABLE IV                                    __________________________________________________________________________               9           10          11                                                    GLASS                                                                              GRAPHITE                                                                             GLASS                                                                              GRAPHITE                                                                             GLASS                                                                              GRAPHITE                              __________________________________________________________________________    WINDING SPEED = 12 in./sec.                                                   PART       GOOD GOOD   POOR GOOD   GOOD GOOD                                  CONSOLIDATION                                                                 DRIP DURING                                                                              NO   NO     YES  YES    NO   YES                                   HEAT CURE                                                                     WINDING SPEED = 20 in./sec.                                                   PART       GOOD --     POOR --     GOOD --                                    CONSOLIDATION                                                                 DRIP DURING                                                                              NO   --     YES  --     NO   --                                    HEAT CURE                                                                     __________________________________________________________________________

Composition 9, representing the amine curing resin of the presentinvention, was found to be free of drip and maintained uniformity ofresin distribution throughout the substrate layers.

Composition 10, representative of those exemplified in theabove-mentioned patent to Green, was found not to be useful for windingapplications in accordance with the present invention. The results ofthe heat-cure demonstrated observable dripping and loss of uniformity inthe resin distribution. The Green composition does not employ peroxidesin accordance with the present invention. Instead, Green uses benzyldimethyl acetal, described as a photopolymerization catalyst.

Composition 11 is representative of a composition similar to the aminecuring resin of the present invention, but lacking the peroxide. Theresin without peroxide exhibited variable results, as shown in Table IVabove. When applied to graphite fiber, Composition 11 showed significantresin drip upon heat cure. However, when applied to glass fiber, atwinding speeds of both 12 and 20 in./sec., the resin provided good partconsolidation and no significant resin drip upon heat cure. It isbelieved that the glass fiber transmits sufficient UV light for theresin to gel even in the absence of the peroxide. But the compositionwithout a peroxide is not effective as an amine curing resin for theimpregnation of UV-opaque fibers.

Compositions 4 (Example 1) and 8 (Example 2), employing t-butylperbenzoate with a T_(1/2) of 104° C., demonstrate performancesubstantially comparable to Composition 11 having no peroxide at all.These compositions are less effective for applications involvingUV-opaque fiber, such as carbon fiber, and they are therefore lessdesirable. It is apparent from these experiments that the presence ofperoxides having the requisite 10 hour T_(1/2) of less than 104° C.enable the creation of a filament wound composite which has non-dripcapability during the heat-cure stage.

EXAMPLE 4

Table V, below, summarizes a comparison of the viscosities of the resinsof the present invention (Compositions 13 and 14) against the viscosityof a resin described by the aforementioned Drain et al. patent(Composition 12). The viscosities of Compositions 12-14 were determinedby measuring the viscosity of 75 gram samples of each composition on aBrookfield DV I viscometer, using a 25° C. water bath. The two resinexamples of the present invention retain commercially useful lowviscosities, i.e., <2000 cps, for at least eight hours at ambient lightand temperature, while the Drain et al. composition becomes unworkablewithin two hours. It is apparent therefore that the compositions of thepresent invention possess the significant advantage of relatively longpot-life. A long resin pot-life is desirable for practical industrialuse since it can eliminate the need for two component mixing/meteringmachines and their associated clean up and maintenance problems.

Table V, below, also provides a comparison of the glass transitiontemperatures (T_(g)) of the resin compositions of the present invention(Compositions 13 and 14) with that of a resin of the Drain et al. patent(Composition 12). Compositions 13 and 14 have T_(g) s of 120° C. and152° C., respectively, while Composition 12 has a T_(g) of 80° C. Thehigher glass transition temperatures of the compositions of the presentinvention provide greater temperature resistance when used in fibercomposite articles, and unlike the resins of Drain et al., are useful inhigher temperature applications.

                                      TABLE V                                     __________________________________________________________________________                            12       13        14                                                         DRAIN ET AL.                                                                           AMINE CURING                                                                            ANHYDRIDE CURING                                           RESIN    RESIN     RESIN                                                      PHR      PHR       PHR                                __________________________________________________________________________    EPOXY MATERIALS                                                               2,2-BIS(GLYCIDYLOXYPHENYL)                                                                            100      100       100                                PROPANE*                                                                      DIGLYCIDYL ETHER OF     --       100       --                                 BISPHENOL A*                                                                  CYCLOALIPHATIC EPOXIDE* --       --        18                                 ACRYLATE MATERIALS                                                            DPMP*                   20       --        21                                 HEXANEDIOL DIACRYLATE   --       20        10                                 HYDROXYPROPYL METHACRYLATE                                                                            --       --        12                                 T-BUTYL PERBENZOATE     2        2         2                                  HYDROXYMETHYLPHENYL PROPANONE                                                                         1        4         5                                  DIAMINO POLYPROPYLENE OXIDE*                                                                          20       --        --                                 ETHYL METHYL IMIDAZOLE  --       7.5       0.5                                NADIC METHYL ANHYDRIDE  --       --        124                                VISCOSITY (cps)                                                               0 HOUR                  960      660       640                                2 HOURS                 10,000   --        --                                 8 HOURS                 260,000  1270      --                                 24 HOURS                SOLID    3610      1070                               Tg (°C.)         80       120       152                                __________________________________________________________________________     *The 2,2bis(glycidyloxyphenyl) propane used in for Examples 12-14 was EPO     828 available from Shell Chemical Co. The diglycidyl ether of Bisphenol A     was EPON 825 also available from Shell Chemical Co. The cycloaliphatic        epoxide used was ERL4221 available from Union Carbide Co. DPMP is an          abbreviation for dipentaerythritol monohydroxy pentaacrylate. The diamino     polypropylene oxide used in the examples was Jeffamine D230 available fro     Texaco.                                                                  

EXAMPLE 5

This example is intended to demonstrate, using thermogravimetricanalysis, that the compositions and processes of the present inventionallow for non-drip properties during heat cure. Through the use ofthermogravimetric analysis, the uniformity of resin distribution can bedetermined, thereby evidencing the non-drip feature.

The data shown in Table VI are the results of a comparison of twofilament windings using an amine curing resin composition of the presentinvention. The amine curing composition was prepared according to theprocedures described herein using 74.4 wt. % diglycidyl ether ofBisphenol A, 5.6 wt. % ethyl methyl imidazole, 14.9 wt. % neopentylglycol diacrylate, 1.5 wt. % t-amylperoxy-2-ethyl-hexanoate, 3.0 wt. %2-benzyl-2-methyl-1-phenyl-propan-1-one, along with 0.5 wt. % defoamingagent and 0.1 wt. % wetting agent. Filament winding was performed ingeneral accordance with the procedures described above. Fiberglass wasimpregnated at a speed of 12 in./sec. and formed into articles bywinding onto two separate mandrels. One winding was exposed to UV lightat an intensity of 120 mW/cm². Another winding was not exposed to UVlight. Both articles were heat-cured without rotation for 2 hours at150° C.

                  TABLE VI                                                        ______________________________________                                                           UV                                                                            AND   HEAT                                                                    HEAT  ONLY                                                 ______________________________________                                        RESIN WT. % - TOP    25.7    24.7                                             RESIN WT. % - BOTTOM 25.6    30.0                                             DRIP                 NO      YES                                              ______________________________________                                    

The data in Table VI are the results of thermogravimetric analysis (TGA)of the heat-cured articles. TGA was performed in accordance with theprinciples described in W. W. Wendlandt and P. K. Gallagher,"Instrumentation", Chapter 1 of Thermal Characterization of PolymericMaterials, E. A. Turi, ed., Academic Press, 1981.

The resultant articles were then subjected to thermogravimetric analysisfor determination of uniformity of resin distribution. Sections of thetop and bottom of the wound article were cut off, weighed, and theweighed samples then heated slowly to a temperature of 800° C., atemperature sufficient to burn off the resin coating leaving the heatresistant fiber behind. During the heating process, the samples weightsare monitored by the instrument. The final difference in the weights ofthe sample before and after heating, provides a measure of the quantityof resin present in the sample. Uniformity of resin distribution isindicated if the resin proportion of each sample is substantiallyidentical. If a substantial difference in sample weights is observed,then the resin is deemed to have been distributed non-uniformly on thearticle due to excessive resin flow and drip during heat cure.

If desired, the uniformity of the coating of the resin onto the fibermay be determined prior to winding of the coated fiber onto a mandrel.However, it will be noted by those having skill in the art that anyinitial irregularity or non-uniformity of resin coating on the fiberwill not affect the uniformity of the wound article because of theability of the gelled resin to flow and merge with overlapping resinduring winding onto the mandrel.

Samples were taken from the top and bottom portions of each article. TheTGA results show that the article initially cured by UV exposureretained uniform resin distribution without the necessity for rotatingthe part during the heat-cure step. Furthermore, no resin drip wasobserved on the UV cured article. The data also show that in the absenceof UV exposure the resin will flow from the top portion of the articleto the bottom, and that the resin will also drip during the heat-cure.The article will thereby become substantially anisotropic.

EXAMPLE 6

A further example of the anhydride curing compositions of the presentinvention is shown below in Table VII. Fiberglass articles made usingthis composition were UV cured and then heat cured, preferably byheating at 170° C. for 1 hour.

                  TABLE VII                                                       ______________________________________                                                                  WT. %                                               ______________________________________                                        RESIN COMPONENT                                                               DIGLYCIDYL ETHER OF BISPHENOL A                                                                         57.47                                               CYCLOALIPHATIC EPOXIDE*   11.77                                               MODIFIED DIGLYCIDYL ETHER 9.98                                                OF BISPHENOL A*                                                               DPMP*                     10.21                                               HYDROXYPROPYL METHACRYLATE                                                                              3.31                                                T-BUTYL PERBENZOATE       1.19                                                WETTING AGENT             0.12                                                METHYL IMIDAZOLE          5.85                                                TOTAL                     100.00                                              ANHYDRIDE COMPONENT                                                           NADIC METHYL ANYDRIDE     98.92                                               PHOTOINITIATOR            1.08                                                TOTAL                     100.00                                              ______________________________________                                         *In Table VII, the cycloaliphatic epoxide used was ERL 4221 available fro     Union Carbide Co. The modified diglycidylether of Bisphenol A was EPIREZ      5027 available from Rhone Poulenc. DPMP is an abbreviation for                dipentaerythritol monohydroxy pentacrylate. The photoinitiator used was       2benzyl-2-dimethylamino-1-[4(4-morpholinyl)phenyl1-butananone.           

While the invention has been described with reference to specificembodiments, it will be apparent that numerous variations, modificationsand embodiments are possible, and accordingly all such variations,modifications and embodiments are to be regarded as being within thespirit and scope of the present invention.

What is claimed is:
 1. A filament winding composition comprisinga. anepoxy component including at least one polyepoxide resin curable byheat; b. an olefinically unsaturated monomer component including atleast one polyolefinically unsaturated monomer curable by actinicradiation; c. at least one photoinitiator which is not a peroxide havinga ten hour decomposition half-life at temperatures from about 50° toless than about 104° C. d. at least one heat activated organic peroxidefor said olefinically unsaturated monomer component, said peroxidehaving a ten hour decomposition half-life at temperatures from about 50°C. to less than about 104° C. and which is substantially unreactive inthe presence of actinic radiation and in the absence of aphotosensitizer; and e. at least one heat activated curing agent forsaid epoxy component, comprising(i) at least one carboxylic acidanhydride; and (ii) at least one anhydride accelerator compound, whereinsaid composition when immobilized with actinic radiation and furtherheat-cured without substantial resin drip yields a T_(g) of at leastabout 110° C.
 2. The composition of claim 1 wherein the organic peroxideis selected from the group consisting diacylperoxides,peroxydicarbonates, peroxyesters, peroxyketals and mixtures thereof. 3.The composition of claim 1 wherein the organic peroxide is selected fromthe group consisting of lauroyl peroxide, t-amylperoxy-2-ethylhexonateand 1,1-di(t-butylperoxy)-3,3,5-trimetyhylhexane.
 4. The composition ofclaim 1 wherein the organic peroxide is included in an amount of fromabout 0.2 wt. % to about 2 wt. %.
 5. The composition of claim 4 whereinthe organic peroxide is included in an amount of from about 0.3 wt. % toabout 1.0 wt. %.
 6. The composition of claim 1 wherein the polyepoxideresin is selected from the group consisting of polyglycidyl andpoly(β-methylglycidyl)ethers of dihydric and polyhydric alcohols andphenols, novolaks, alkyl-substituted phenols and halogen-substitutedphenols, poly(N-glycidyl) compounds obtained from amines obtained fromamines containing at least two amino-hydrogen atoms,triglycidylisocyanurate, N,N'-diglycidyl derivatives of cyclic alkalineureas and hydantoins, poly(S-glycidyl) derivatives of dithiols andmixtures thereof.
 7. The composition of claim 6 wherein the polyepoxideresin is selected from the group consisting of diglycidyl ethers ofbisphenols.
 8. The composition of claim 1 wherein the polyepoxide resinis included in an amount of from about 37 wt. % to about 48 wt. %. 9.The composition of claim 8 wherein the polyepoxide resin is included inan amount of from about 40 wt. % to about 45 wt. %.
 10. The compositionof claim 1 wherein the polyolefinically unsaturated monomer is selectedfrom the group consisting of acrylic and methacrylic resins, vinylmonomers, unsaturated polyesters solubilized in vinyl monomers andmixtures thereof.
 11. The composition of claim 10 wherein thepolyolefinically unsaturated monomer is selected from the groupconsisting of trimethylolopropane trimethacrylate, trimethylolpropanetriacrylate, dipentaerythritol monohydroxypentaacrylate, pentaerythritoltriacrylate, ethoxylated trimethylolpropane triacrylate, 1,6-hexanedioldiacrylate, neopentyl glycol diacrylate, pentaerythritol tetraacrylate,and 1,3-butylene glycol diacrylate.
 12. The composition of claim 1wherein the polyolefinically unsaturated monomer is included in anamount of from about 10 wt. % to about 30 wt. %.
 13. The composition ofclaim 12 wherein the polyolefinically unsaturated monomer is included inan amount of from about 10 wt. % to about 20 wt. %.
 14. The compositionof claim 1 wherein the photoinitiator is selected from the groupconsisting of benzophenone and substituted benzophenones, acetophenoneand substituted acetophenones, benzoin alkylethers, xanthone andsubstituted xanthones, camphoroquinone peroxyesters, 9-fluorenecarboxylic acid peroxyesters and mixtures thereof.
 15. The compositionof claim 14 wherein the photoinitiator is selected from the groupconsisting of benzoin, 2-hydroxy-2-methyl-1-phenyl-propan-1-one and2-benzyl-2-(dimethylamino)-1-[4-(4-morpholinyl)phenyl]-1-butanone. 16.The composition of claim 1 wherein the photoinitiator is included in anamount of from about 1 wt. % to about 10 wt. %.
 17. The composition ofclaim 16 wherein the photoinitiator is included in an amount of fromabout 1.5 wt. % to about 5 wt. %.
 18. The composition of claim 1 whereinthe carboxylic acid anhydride is selected from the group consisting ofmethyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride,chlorendic anhydride, nadic methyl anhydride and mixtures thereof. 19.The composition of claim 1 wherein the anhydride is included in anamount of from about 33 wt. % to about 43 wt. %.
 20. The composition ofclaim 19 wherein the anhydride is included in an amount of from about 36wt. % to about 41 wt. %.
 21. The composition of claim 1 wherein theanhydride accelerator is selected from the group consisting ofdicyandiamide, boron trifluoride:amine complexes, borontrichloride:amine complexes, latent amine curatives, tertiary amines,aromatic polyamines, imidazoles and mixtures thereof.
 22. Thecomposition of claim 21 wherein the anhydride accelerator is selectedfrom the group consisting of benzyl dimethylamine,1-(2-cyanoethyl)-2-ethyl-4-methylimidazole, 2-ethyl-4-methyl imidazole,and 2,4-diamino-6 [2'-methylimidazolyl-(1)']ethyl-s-triazineisocyanurate adduct.
 23. The composition of claim 1 wherein theanhydride accelerator is included in an amount of from about 0.1 wt. %to about 5.0 wt. %.
 24. The composition of claim 1 wherein saidcomposition has an initial viscosity of about 2000 centipose or less andis capable of retaining said viscosity for at least about 2 hours at atemperature of from about ambient temperature to about 60° C.
 25. Thecomposition of claim 1 wherein said viscosity remains from about 300centipoise to about 2,000 centipoise for a minimum of about 6 hours at atemperature of from about ambient temperature to about 60° C.